Size and weight are big decision factors when you are trying to find the ideal camera for your needs.
In this section, we are going to illustrate the Olympus SZ-12 and Olympus E-PL1 side-by-side from the front, back and top in their relative dimensions. Olympus SZ-12 has external dimensions of 106 x 69 x 40 mm (4.17 x 2.72 x 1.57″) and weighs 226 g (0.50 lb / 7.97 oz) (including batteries). Olympus E-PL1 has external dimensions of 115 x 72 x 42 mm (4.53 x 2.83 x 1.65″) and weighs 334 g (0.74 lb / 11.78 oz) (including batteries).
Below you can see the front-view size comparison of the Olympus SZ-12 and the Olympus E-PL1. Olympus SZ-12 is clearly the smaller of the two cameras. Its body is 9mm narrower, 3mm shorter and 2mm thinner than Olympus E-PL1. As you can tell, actually this is not a fair size comparison since Olympus SZ-12 has a built-in lens but Olympus E-PL1 doesn't. Once you put a lens on E-PL1, its thickness will increase significantly.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Olympus SZ-12 is significantly lighter (108g ) than the Olympus E-PL1 which may become a big advantage especially on long walking trips.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on E-PL1, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Olympus SZ-12 nor Olympus PEN E-PL1 provides any type of weather sealing in their bodies, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top Compact Cameras with Weather Sealing Top Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Olympus SZ-12's 3.00" LCD screen is slightly larger than Olympus E-PL1's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.